[tankbot]

> And that's because the cut-off is not biological, it's social.

I disagree. There is a wealth of biological evidence to show that a human's brain doesn't finish maturing until (approx.) age 25. By that standard you could make the argument that 25 is when people reach adulthood.

Of course, what we're really talking about here is expectations of responsibility, so even though "by 15 or 16 people should already be expected to act like adults" these young people still have maturing to do.

It's not surprising that in our rich modern society the age of 'adulthood' has risen to 25, especially considering we live so much longer than we used to.

[ars]

Why is the definition of adulthood "finish maturing"? If anything that should be middle age, i.e. in the middle of adulthood, not the start of it.

By your definition as soon as someone becomes an adult they start degrading in mental ability. The peak of mental ability should match the middle of the productive years.

But in any case the maturity of the brain is not just biologically controlled - it's environmentally controlled. The brain of someone treated like an adult will be more mature than that of someone teated like a child.

The brain responds to stimulus, it doesn't really have a pre-programmed makeup. It has basic abilities, but that ones that are expressed are the ones that it needs/uses.

[tankbot]

All fair points, but I never defined adulthood, only disagreed with the parent which stated "the cut-off is not biological, it's social". Of course there are social factors as well as biological. I'm sure I'm not qualified to form such a definition, though if I tried it would have to include many factors.

I, for example, moved out of my parents' house at 18, but I wouldn't say I became an 'adult' until at least my early 30's. Even now I feel like a kid most of the time, in spite of my many responsibilities - even with a kid of my own!

I don't think we ever finish maturing, and I think we never stop learning, even though our 'peak' mental ability may come and go.

[rwallace]

There is also a wealth of biological evidence to show that a human's brain and body start deteriorating significantly before age 25; you can pick and choose the evidence that supports the conclusion you want.

In practice, our supposedly rich modern society is becoming mentally unhealthy to a degree that increasingly outweighs the material gains of recent generations; mental illness is common, suicide has become a major cause of death among young people, birthrate has crashed below extinction level. We can fix what we are doing wrong - a large part of which is treating young people like prize animals in gilded cages - or our society can end up in Darwin's bit bucket. We can decide which of these options we prefer, but I don't see the universe giving us the option of "neither".

[apsec112]

http://rationalconspiracy.com/2012/09/10/age-and-brain-devel...

[tankbot]

Can't trust that graph because the x axis doesn't start at 0 ;)

[jlgreco]

A valid objection, but is it really meaningful to talk about intelligence of toddlers in the same context as intelligence of other people? I mean, they're still figuring out that they have hands, and that they control them.

[tankbot]

No, it was sarcasm.

[Shish2k]

> There is a wealth of biological evidence to show that a human's brain doesn't finish maturing until (approx.) age 25

"Finish maturing" as in "can no longer teach the old dog new tricks"? Even more reason to give them practice in adult skills before then IMO